Double-Anchor Dyes

The first group includes structures in which two monochlorotriazine units are connected by a suitable bridge (e.g., 12). The synthetic approach to these compounds makes it possible to combine two different chromophores in a single system, opening the way to certain color shades that are not easily accessible via a single chromophore [30], 

The category of reactive dyes with two equivalent anchors also encompasses products containing two vinylsulfonyl or 2-sulfooxyethylsulfonyl groups. An example is C.I. Reactive Black 5, 20505 [17095-24-8] (13), which not only displays a high degree of fixation but is also accessible by a synthetic route that is both simple and economical  

Selective modification of the reactive anchors makes it possible to vary the physical property profile of the dye. 

Mixed-anchor systems in reactive dyes were first described in 1959. Such bifunctional dyes were first marketed in the early 1980s. These products are characterized by two anchors with differing reactivities a more reactive 2-sulfo-hydroxyethylsulfonyl group and a less reactive monochlorotriazinyl residue. An example of such a system is 14  

Warm- and cold-dyeing double-anchor dyes are prepared by incorporating halo-triazinyl and vinylsulfonyl reactive anchors. The bond between the triazine ring and a fiber is stable under basic conditions, whereas that to the vinylsulfonyl group is stable to acid. A combination of the two anchor systems therefore produces a dye with 

---

Other mixed reactive systems have also been patented in addition to the double-anchor dyes so far described, including combinations of monofluorotriazine with difluorochloropyrimidine [32], alkoxychlorotriazine [33], or 2-(sulfothio) ethylsulfonyl groups [34], Other examples incorporate a difluorochloropyrimidine ring in conjunction with a vinylsulfonyl group [35],... 

Dioxazine Dyes. The synthetic routes (see below) to almost all dioxazines yield products with a symmetrical structure, resulting in at least two reactive anchors. The highly reactive double-anchor dyes are suitable for both the exhaust and the padding processes. Ecological limits for wastewater are satisfied as a result of a high degree of fixation and low salt requirements in the exhaust process, whereby the latter also has a positive influence on leveling. 

An important step forward was achieved with the introduction of double- or multiple-anchor dyes. These can be homo- or heterofunctional (mixed-anchor systems). When dyes are provided with anchors of different reactivity, a wide range of dyeing properties can be realized. At the same time, process reliability and dyefastness are improved. Thus far, combination of the triazine and vinylsulfone anchors has had the best effect. 

Because of their symmetry, all such triphenodioxazine reactive dyes feature double or even fourfold anchor systems. However, dyes with only one anchor group can be prepared by adding a single equivalent of acylating agent. Most asymmetric products of this type are based on l,4-phenylenediamine-2-sulfonic... 

Mao J, He N, Ning Z et al (2012) Stable dyes containing double acceptors without COOH as anchors for highly efficient dye-sensitized solar cells. Angew Chem Int Ed 51(39) 9873-9876... 

---